多胞材料的动态应力应变状态及其抗爆性能分析

发布时间：2018-06-15 18:28

本文选题：多胞材料 + 应力波　；参考：《中国科学技术大学》2016年博士论文

【摘要】：多胞材料具有优越的抗爆炸抗冲击性能,常被用作车辆,高铁,航空航天等领域的能量吸收结构和耐撞装置。在准静态加载速率下,多胞材料的应力应变曲线呈现出弹性段、平台段和压实段,且该应力应变曲线可以认为是多胞材料在准静态下的本构行为。在动态冲击下,多胞材料的力学行为表现出变形局部化和应力增强两个特征,但其动态应力应变曲线到目前为止并不清楚。最近,Zheng等通过细观有限元模型结合局部应变场和边界应力得到了多胞材料在高速冲击下的应力应变状态点,并提出了相应的率相关、刚性-塑性硬化(D-R-PH)冲击波模型,但该研究也仅仅适用于高速冲击下的情形。在中等冲击速度下,多胞材料的变形模式不再是逐层压溃的压缩行为,很难再通过单一的冲击波理论来进行近似表征,故在中等冲击速度下的多胞材料的力学行为研究变得极为困难。本文利用波传播法(该方法不需要依赖于材料本构或冲击波假定)研究多胞材料在动态冲击下的应力应变状态点,揭示了多胞材料在不同冲击速度下的应力应变曲线,并得到了一条完整的、唯一的动态应力应变曲线。除此之外,本文还探究了多胞牺牲层在爆炸载荷下的动态力学性能,并提出了多胞牺牲层临界长度的经验公式和渐近解。波传播法是通过材料试样传播信息结合初始/边界条件来反推材料的应力应变曲线的一种方法,其最大优势为不需要提前引入材料试样的本构假定。本文基于多胞材料的细观有限元模型的Taylor冲击实验,通过Lagrangian分析法(一种波传播法)研究了多胞材料的动态力学行为并得到了多胞材料在不同冲击速度下的局部应力应变曲线。局部应力应变曲线呈现出弹性加载,塑性变形和弹性卸载三个阶段,通过提取局部应力应变曲线中卸载段前的临界应力应变状态点,本文得到一条动态应力应变曲线。该动态应力应变曲线与Taylor冲击实验的初速度无关,却依赖于多胞材料的变形模式(准静态,过渡和冲击模式)。与准静态应力应变曲线比较,动态应力应变曲线中的压实段表现出更强的塑性硬化效应,由此可得出多胞材料的率效应在动态冲击研究中并不能被忽略。在冲击模式下,多胞材料的压实应变比准静态下的应变大很多,该现象表明在动态冲击下,多胞材料被压得更加密实；而在过渡模式下,多胞材料的动态应力明显比准静态应力高,表明在过渡模式下的局部惯性效应并不能忽略。本文还进一步分析了多胞材料的应变率敏感性和速率敏感性,结果表明多胞材料的初始压溃应力表现出明显的应变率敏感性,而压实段呈现出速率敏感性。在高速冲击下,多胞材料的动态行为可以通过冲击波模型近似表征。然而许多冲击波模型参数确定均基于多胞材料的准静态应力应变曲线,并没有考虑动态下的应力应变特征。本文通过提取多胞材料在动态冲击下的特征关系,如冲击波速度和冲击速度之间的关系,波后应变和冲击速度之间的关系等,分析各个冲击波模型的合理性和可靠性。结果表明在高速冲击下,率相关、刚性-塑性硬化模型能很好地表征多胞材料的动态行为。根据跨过冲击波波阵面的守恒条件,给出了反测多胞材料的D-R-PH冲击波模型参数的实验方法。在应用方面,多胞材料具有优越的能力吸收和抗爆炸性能。本文采用刚性-塑性硬化模型(R-PH)分析了多胞牺牲层在爆炸载荷下的力学性能。对多胞牺牲层在三角爆炸载荷作用下的应力波传播建立了一维冲击波模型,得到了冲击波在多胞牺牲层中传播的控制方程,并揭示了冲击波在多胞牺牲层中的传播特征。通过参数分析法揭示了多胞牺牲层中附加质量块质量和爆炸载荷强度对牺牲层设计结果的影响。本文还将基于刚性-塑性硬化模型(R-PH)和刚性-理想塑性-锁定模型(R-PP-L)设计的多胞牺牲层的抗爆炸性能进行对比,说明基于R-PP-L模型设计的多胞牺牲层存在着风险性和不合理性。多胞牺牲层的临界长度,即牺牲层恰好吸收完爆炸载荷时的长度,为工程设计比较关心的一个指标。因此,本文通过量纲分析研究了多胞牺牲层临界长度,分析结果表明多胞牺牲层临界长度主要跟三个无量纲参数有关系,并通过控制变量法得到了多胞牺牲层的经验公式。本文进一步通过正则摄动法分析得到了多胞牺牲层临界长度的渐近解。然而,复杂的渐近解形式将限制其在工程设计中的应用,所以本文建议在工程设计中应当选择形式简单的经验解作为多胞牺牲层的临界长度设计标准。最后,通过基于三维Voronoi技术的细观有限元模型验证了基于R-PH材料模型的多胞牺牲层的设计准则。
[Abstract]:Multi cell materials have excellent anti blast resistance and are often used as energy absorption structures and crashworthiness devices in vehicles, high speed iron, aerospace and other fields. Under quasi static loading rate, the stress-strain curves of multi cell materials show elastic segments, platform segments and compaction sections, and the stress strain curves can be considered as quasi static multi cell materials. Under dynamic impact, the mechanical behavior of multi cell materials shows two characteristics of deformation localization and stress enhancement, but the dynamic stress-strain curve is not clear so far. Recently, Zheng and so on through the mesoscopic finite element model combined with the local strain field and boundary stress to get the multi cell material under high speed impact. In the stress strain state point, the corresponding rate correlation, the rigid plastic hardening (D-R-PH) shock wave model is proposed, but the study is only applicable to the case under high velocity impact. Under the medium impact velocity, the deformation mode of the multi cell material is no longer the compression behavior of the laminating pressure, and it is difficult to use the single shock wave theory to make the approximate table. It is very difficult to study the mechanical behavior of multi cell materials at medium impact velocity. In this paper, the stress strain state of multi cell materials under dynamic impact is studied by wave propagation method (this method does not depend on material constitutive or shock wave hypothesis), and the stress-strain curves of multi cell materials under different shock velocities are revealed. A complete, unique dynamic stress-strain curve is obtained. In addition, the dynamic mechanical properties of the multi cell sacrificial layer under the explosive load are also explored, and the empirical formula and asymptotic solution of the critical length of the multi cell sacrificial layer are proposed. The wave propagation method is used to reverse the material through the material sample propagation information combined with the initial / boundary conditions. A method for the stress-strain curve of the material is the greatest advantage of the constitutive assumption that the material specimen is not needed in advance. Based on the Taylor impact test of the meso finite element model of the multi cell materials, the dynamic mechanical behavior of the multi cell materials is studied by Lagrangian analysis (a wave propagation method) and the multi cell materials are obtained in different types. The local stress-strain curve under the impact velocity. The local stress-strain curve shows three stages of elastic loading, plastic deformation and elastic unloading. By extracting the critical stress and strain state point before the unloading section of the local stress strain curve, a dynamic stress-strain curve is obtained. The dynamic stress-strain curve and the Taylor impact compaction curve are obtained. The initial velocity is independent of the initial velocity, but depends on the deformation mode of multi cell materials (quasi-static, transition and impact modes). Compared with the quasi-static stress-strain curve, the compaction section in the dynamic stress-strain curve shows a stronger plastic hardening effect. Thus, the rate effect of multi cell materials can not be ignored in the dynamic impact study. Under the model, the compacted strain of multi cell material is much larger than that under quasi-static strain. This phenomenon indicates that under dynamic impact, the multi cell material is compacted more densely, and the dynamic stress of multi cell material is obviously higher than that of quasi-static stress in the transition mode, which indicates that the local inertia effect in the transition mode can not be ignored. The strain rate sensitivity and rate sensitivity of multi cell materials are analyzed. The results show that the initial crushing stress of multi cell materials shows obvious strain rate sensitivity, while the compaction section shows the rate sensitivity. Under the high velocity impact, the dynamic behavior of multi cell materials can be approximated by the shock wave model. However, many parameters of the shock wave model are parameters. The quasi static stress-strain curve based on multi cell materials is determined, and the dynamic stress-strain characteristics are not taken into account. In this paper, the relationship between the dynamic impact of multi cell materials, such as the relationship between the velocity of shock wave and the velocity of shock, the relationship between the post wave strain and the impact velocity, is extracted, and the rationality of the shock wave model is analyzed. The results show that the rigid plastic hardening model can characterize the dynamic behavior of multi cell material well under the high velocity impact, and the rigid plastic hardening model can well characterize the dynamic behavior of the multi cell materials. According to the conservation conditions of the cross impact wave front, the experimental method of the D-R-PH shock wave model parameters of the multi cell material is given. The mechanical properties of the multi cell sacrificial layer under the explosive load are analyzed by the rigid plastic hardening model (R-PH). The one-dimensional shock wave model is established for the propagation of the stress wave of the multi cell sacrificial layer under the triangle explosion load, and the control equation of the shock wave propagating in the multi cell sacrificial layer is obtained, and the impact is revealed. The influence of the mass of mass and the strength of the explosive load on the design results of the sacrificial layer in the multi cell sacrificial layer is revealed by the parameter analysis method. The anti explosion properties of the multi cell sacrificial layer based on the rigid plastic hardening model (R-PH) and the rigid ideal plastic locking model (R-PP-L) are also designed in this paper. The comparison shows that the multi cell sacrificial layer based on the R-PP-L model has the risk and unreasonableness. The critical length of the multi cell sacrificial layer, that is, the length of the sacrificial layer exactly absorbs the length of the explosion load, is a more concerned indicator for the engineering design. Therefore, the critical length of the multi cell sacrificial layer is studied by the dimensional analysis, and the analysis of the critical length of the multi cell sacrificial layer is analyzed. The results show that the critical length of the multi cell sacrificial layer is mainly related to the three dimensionless parameters, and the empirical formula of the multi cell sacrificial layer is obtained by the control variable method. In this paper, the asymptotic solution of the critical length of the multi cell sacrificial layer is obtained by the canonical perturbation method. However, the complex asymptotic form will limit its engineering design. Therefore, this paper suggests that in engineering design, a simple form of empirical solution should be chosen as the critical length design standard for the multi cell sacrificial layer. Finally, the design criteria of the multi cell sacrificial layer based on the R-PH material model are verified by the mesoscopic finite element model based on the three-dimensional Voronoi technology.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TB301

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